Radio-based communications systems are increasingly used to transmit important information. In order to ensure the reliability of such transmissions, and to prevent the public or unauthorized distribution of proprietary or confidential information, various techniques have been developed. For example, frequency hopping, spread spectrum, encryption, and other transmission and encoding technologies can be used. Although such techniques can be effective at increasing the reliability and security of radio transmissions, improved reliability, data rates, and range continue to be sought after.
In any radio communication system, the signal-to-noise ratio is an important consideration. The strength of the received signal can be affected by various factors, such as the transmission range, antenna gain, filter efficiency, environmental conditions, encoding techniques, transmission strength, and the like. Noise can originate from natural sources, intentional interference, and unintended interference.
Various techniques can be employed in order to increase the signal strength of a desired signal or to reduce the effect of noise on a desired signal. For example, the transmission power of the signal can be increased, coding techniques can be improved, data rates can be reduced, signal processing can be improved, antenna gain can be increased, or antennas capable of forming beams directed towards a desired signal or conversely capable of placing a null in a direction corresponding to a source of noise can be used. However, the ability of such techniques to improve the signal to noise ratio of a desired signal is limited. For example, available transmission power can be constrained by the ability of a transmitter to access a suitable power supply. Security considerations associated with data encoding can place limits on the efficiency of such encoding. Reductions in data rates can be impractical or undesirable. Improvements to the gain of an antenna can be limited by size and other physical antenna constraints.
Manipulating the shape of an antenna beam can be an effective way to improve the signal-to-noise ratio. However, doing so has required identifying the relative location of a noise source or sources, and accurately modifying the beam shape to exclude the noise source or sources. This can be difficult to accomplish across a broad frequency range as such beam steering techniques have required large amounts of processing power.